Interobserver Variability in Cardiovascular FDG PET/CT Analysis in Large Vessel Vasculitis.

Area of Science:

• Cardiovascular Imaging
• Nuclear Medicine
• Rheumatology

Background:

• Positron Emission Tomography/Computed Tomography (PET/CT) is valuable for diagnosing and monitoring large vessel vasculitis.
• Standardized uptake values (SUV) are used to quantify tissue uptake in PET/CT, but their reproducibility in vascular structures needs further study.
• COVID-19 infection can be associated with large vessel vasculitis, necessitating reliable imaging assessment.

Purpose of the Study:

• To evaluate the inter-observer variability of qualitative visual grading and quantitative standardized uptake values (SUVmean and SUVmax) of aortic ¹⁸F-FDG uptake.
• To assess the reproducibility of these measurements in patients with COVID-19 related large vessel vasculitis.

Main Methods:

• A sub-study of the COSMIC-19 trial involving 30 patients with mild to moderate COVID-19.
• Combined Computed Tomography Coronary Angiogram and ¹⁸F-FDG PET/CT followed by cardiac magnetic resonance.
• Two independent observers measured SUVmean and SUVmax in five regions of interest along the aorta on axial slices.

Main Results:

• Excellent inter-observer agreement was observed for qualitative visual grading of aortic ¹⁸F-FDG uptake (kappa coefficients > 0.90).
• High positive correlations were found between observers for quantitative SUVmean measurements in the ascending aorta (r=0.96), aortic arch (r=0.90), and descending aorta (r=0.91).
• Quantitative SUVmax measurements also demonstrated substantially strong inter-observer reproducibility.

Conclusions:

• There is excellent inter-observer reproducibility for both qualitative and quantitative ¹⁸F-FDG measurements of aortic uptake in patients with COVID-19 related large vessel vasculitis.
• Standardized uptake value (SUV) measurements, particularly SUVmean, are reliable for assessing vascular inflammation in this patient group.
• The findings support the use of PET/CT with SUV measurements for monitoring disease activity and progression in large vessel vasculitis associated with COVID-19.